Recommended Specifi- 
cations for Reinforced 
Concrete Design 

Based on the Regulations in the Building 
Code Recommended by the National 
Board of Fire Underwriters and the 1916 
Report of the Joint Committee on 
Concrete and Reinforced Concrete 



'* Concrete for Permanence 



Published by 

Portland Cement Association 

111 West Washington Street 
Chicago 



NOVEMBER, 1916 



ATLANTA 

DALLAS 

I N Dl AN APOLIS 

KANSAS CITY 



N EW YORK 

PARKERSBURC, VV. VA. 

PITTSBURGH 

SAN FRANCISCO 



-xK 



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Note 

The following specifications are recommended for use in 
designing buildings of reinforced concrete to be erected in 
cities not having a building ordinance. 

If alternative designs are to be submitted, these specifications 
should accompany the architect's plans and details, and be 
headed by the following clause: 

"This building has been designed in accordance 
with the following specifications. Intending bidders 
wishing to submit alternative designs must follow 

strictly the design specifications and deposit 3 

with bid to cover cost of checking said alternative 

design, which checking will be done by 

of 

The deposit of unsuccessful bidders will be returned 
when the contract is awarded." 

Portland Cement Association, 

111 West Washington Street, 
Chicago. 
November, 1916. 



Recommended Specifications for 
Reinforced Concrete Design 



LOADS 

The schedule of superimposed uniform (live) loads per square foot is 
as follows: 

Roof pounds per square foot. 

floor pounds per square foot. 

floor pounds per square foot. 

Etc. 

The roof slab, together with the roof beams and girders, shall be 
designed to carry the full live and dead loads. All floor slabs and beams 
shall be designed to carry the full live and dead loads. All girders under 
floors where the assumed live load is under 120 pounds per square foot 
shall be designed to carry all the dead load and 85 per cent of the assumed 
live load. No deduction for floor loads greater than 120 pounds per 
square foot. 

Every column, post or other vertical support shall be of sufficient 
strength to bear safely the combined live and dead loads transmitted to it. 
The following reductions are permissible when the live loads are under 
120 pounds per square foot: 

For columns supporting roof: No reduction. 

For columns supporting top floor: A reduction of 10 per cent of the live load 

of the top floor may be made. 
For columns supporting each succeeding floor: A reduction of 5 per cent of the 
live load per floor may be made, but the maximum deduction for any floor 
shall not exceed 50 per cent. The reductions shall cease when a floor carry- 
ing a live load of more than 120 pounds per square foot is reached. 
For-floors, beams, girders and vertical supports carrying machinery: At least 
25 per cent shall be added to the stresses from live loads to provide for 
efl^ect of impact and vibration. 
For sidewalks between the curb and building lines: Live loads shall be taken 
at 300 pounds per square foot or a concentrated load of 5 tons at any point. 

MATERIALS 

Cement: The cement shall meet the requirements of the current 
Standard Specifications for Portland Cement of the American Society for 
Testing Materials. 

Steel: The steel shall meet the requirements of the current Standard 
Specifications for Reinforcing Steel of the American Society for Testing 
Materials. 

3 



RECOMMENDED SPECIFICATIONS FOR REINFORCED CONCRETE DESIGN 

Aggregates and Water: The aggregates and water shall meet the 
requirements of the current specifications for aggregates and water of the 
Portland Cement Association. 

Broken stone or pebble concrete not reinforced shall be assumed as 
weighing 144 pounds per cubic foot, and when reinforced shall be assumed 
as weighing 150 pounds per cubic foot. 

STRESSES 

Extreme fiber stress in compression for 1:2:4 concrete, 650 pounds 
per square inch. For 1: IJ^: 3 concrete, 810 pounds per square inch. 

In direct compression, 1:2:4 concrete, 450 pounds per square inch. 
1: 13^: 3 concrete, 560 pounds per square inch. 

Shearing stress in concrete when diagonal tension is not resisted by- 
steel, 40 pounds per square inch for 1:2:4 concrete and 50 pounds for 
1 : 13^: 3 concrete. 

Unit shearing stress when web reinforcement is used, 120 pounds per 
square inch, of which 40 pounds per square inch may be resisted by the 
concrete. 

In proportioning the section of concrete for shearing stress, the effec- 
tive depth from center of compression area to center of steel area shall be 
used. In beams of T section the width of the stem shall be used. In 
ribbed floors the width of the stem and thickness of flange near supports 
shall be proportioned for cumulative shear on the span. 

Bond stress between concrete and reinforcement, 80 pounds per square 
inch for plain and deformed bars, based on actual section. 

Tensile stress in steel, 16,000 pounds per square inch, for main rein- 
forcement. Tensile stress in stirrup steel, 10,000 pounds per square inch. 

Ratio of deformation of steel to 1: 2: 4 concrete shall be taken as 1: 15 
and to 1: 13^: 3 concrete shall be taken as 1:12. 

Compressive stress in steel shall be equal to the compressive stress in 
the concrete multiplied by the ratio of deformation. 

In continuous beams and slabs the extreme fiber stress in concrete 
in compression may be increased 15 per cent adjacent to supports. 

Bearing on a concrete surface having a total area of at least twice 
the area of the loaded portion may be taken at 700 pounds per 
square inch for 1: 2: 4 concrete and 875 pounds per square inch for 1 : 1}^: 3 
concrete, and, generally, at 35 per cent of the ultimate strength of the 
concrete used, when all other stresses are properly provided for. 

4 



RECOMMENDED SPECIFICATIONS FOR REINFORCED CONCRETE DESIGN 

SLABS, BEAMS AND GIRDERS 

The straight-line method shall be used in designing reinforced concrete. 

The span length for beams simply supported, and for all slabs, shall 
be taken as the distance from center to center of supports, but need not 
be taken to exceed the clear span plus the over-all depth of beam or slab. 
For continuous or restrained beams built monolithically into supports, 
the span length may be taken as the clear distance between faces of sup- 
ports. Brackets shall not be considered as reducing the clear span in the 
sense here intended, and the clear span between T beams is the distance 
face to face of stems. Maximum negative moments are to be considered 
as existing at the end of the span as here defined. 

The bending moments of girders, beams and slabs due to uniformly 
distributed loads shall be taken as not less than: 

1/8 WL, at center when simply supported. 

1/9 fFL, over central support; and 1/10 WL, near the middle of the 
span when continuous for two spans only. 

1/10 /FZ, over first continuous support; and 1/10 WL, near middle 
of end spans when supported at one end and continuous at 
the other end for more than two spans. 

1/12 WL, at center and intermediate supports when continuous over 
more than two supports. 

The simply supported ends of spans shall be reinforced for a negative 
moment of not less than 1/16 WL. 

^= total distributed dead and live loads. 

L ^length of span. 

Floor slabs having supports extending along the four sides shall be 
designed and reinforced as continuous over the supports. For uniformly 
distributed dead and live loads the per cent of load carried on the trans- 
verse span shall be found by subtracting 0.5 from the quotient obtained 
by dividing the length by the breadth. The remainder of the load shall 
be carried on the longitudinal span. If the length of the slab exceeds 1.5 
times its width the entire load shall be carried on the transverse span. 
Using the values thus obtained, each set of reinforcement is to be calcu- 
lated in the same manner as slabs having supports on two supports only, 
using correct depths to center of steel. The amount of reinforcement 
thus determined per foot of width applies only to the middle half of the 
slab and one half of this amount per foot of width may be used in each 
end quarter of the slab. The probable distribution of the loads from two- 

5 



RECOMMENDED SPECIFICATIONS FOR REINFORCED CONCRETZ DESIGN 

way reinforced slabs to supporting beams or girders shall be ascertained, 
and the moments in the beams or girders calculated accordingly. 

The bending moments for slabs or beams with spans of unusual length 
or due to other than uniformly distributed loads shall be more exactly 
computed according to accepted theory. 

In continuous slabs, beams or girders, full provision shall be made for 
the negative bending moments over the supports by placing sufficient 
negative reinforcement near the top of the members to resist the stress. 
This reinforcement shall pass beyond the point of contra-flexure in beams 
or girders and be anchored in the compression concrete of the member 
a sufficient distance to develop the full strength of the steel through bond 
stress. The critical section of continuous construction is over the support. 

Where adequate bond is provided at junction between slab and beam, 
and the two are cast at the same time as a unit, the slab may be considered 
as an integral part of the beam, provided its effective width shall not 
exceed one-fourth of the span length of the beam, nor be greater than 
six times the thickness of the slab on either side of the stem. 

In beams with T sections the width of the stem only shall be used in 
calculating longitudinal shear and -diagonal tension. An effective bond 
shall be provided at the junction of the beam and slab when the principal 
slab reinforcement is parallel to the beam, by the use of transverse rein- 
forcement extending over the beam and well into the slab. 

In the design of T beams acting as continuous beams, sufficient com- 
pression area shall be provided on the under side at the support, either 
by the use of properly designed brackets or by embedding additional 
compression steel in the concrete extending to the point of inflection. 

The minimum thickness of concrete floor slabs shall be 4 inches, and 
of roof slabs 33^^ inches. 

Cement or concrete floor finish shall not be considered in calculating 
the strength of floor members unless it be laid at the same time they are 
cast. 

The design of composite floors consisting of rows of concrete tile or 
hard-burned terra cotta tile, gypsum blocks, sheet steel, or other approved 
fire resisting material, separated by ribs, or beams of reinforced stone 
concrete, shall conform to all the provisions of these specifications so far 
as they are applicable. Not less than 2 bars shall be used in each rib 
with a minimum space between bars of one inch. The width of ribs 
shall be two inches plus the widths of the bars plus the spaces between 
the bars but the minimum width of ribs shall be four inches. 



RECOMMENDED SPECIFICATIONS FOR REINFORCED CONCRETE DESIGN 

The tile or blocks shall be regarded only as fillers, and shall not be 
considered in the design except as a dead load. 

If designed as a T beam, the slab portion above the fillers shall have a 
thickness of at least one-fifth the depth from the top surface to the center 
of the steel and not less than 1}/^ inches, and shall consist of the same 
mixture used for the ribs, and shall be cast at the same time. Under 
these conditions it may be considered in the design of the ribs. 

Tile or block fillers shall be laid with Portland cement mortar joints, 
and shall be thoroughly wet before the concrete is poured. 

The protection for steel bars in the bottom of ribs shall be the same 
as for other beams. 

To resist expansion and shrinkage stresses, reinforcement bars not less 
than 3^ inch diameter shall be placed in the concrete at right angles 
to the ribs and above the fillers, at intervals not exceeding 30 inches. 

Steel reinforcement shall have a minimum protection of concrete on 
all sides as follows: 

In columns and girders, 2 inches; in beams and walls, 13^^ 
inches; and in floor slabs, 1 inch. 

The steel in footings for walls and. columns shall have a mini- 
mum protection of 4 inches of concrete. 

All reinforcement shall be accurately located and mechanically secured 
against displacement during the placing of the concrete. Reinforcement 
bars for slabs shall not be spaced farther apart than two and one-half times 
the thickness of the slab. The spacing of parallel bars in beams shall be 
not less tfean two diameters from center to center, nor less than 1 inch. 
The clear spacing between two parallel layers of bars shall be not less than 
1 inch. In restrained or cantilever construction reinforcement shall 
extend beyond the supports into adjacent construction for full and effective 
anchorage, except that when this is not practicable, anchorage shall be 
obtained by other means acceptable to the {Engineer or Architect). 

Special reinforcement shall be provided to resist concentrated loads. 

Slabs reinforced in one direction only shall have shrinkage rods not 
less than J^-inch in diameter placed above, and crossing the reinforce- 
ment and spaced not over 2 feet apart. 

All reinforcement shall be assembled well in advance of the placing 
of the concrete, and shall be inspected and approved by the {Engineer or 
Architect) before concrete is deposited. 

Splices in reinforcing bars shall be designed to transfer the calculated 
stress at the joint either by bond and shear through the concrete or in 

7 



RECOMMENDED SPECIFICATIONS FOR REINFORCED CONCRETE DESIGN 

vertical supports by bearing between the steel. Splices at points of 
maximum stress shall be avoided where possible. Lap splices of bars 
shall be of sufficient length to develop the required stress in the joint 
without exceeding the bond stress permitted, and the lapped portions 
shall be separated by a space not less than their thickness or a minimum 
of 1 inch. 

Members of web reinforcement in beams shall be designed for diagonal 
tensile stresses, using the calculated vertical shearing stress as a measure 
of these tensile stresses. The longitudinal spacing of vertical stirrups 
shall not exceed one half the depth of beam and that of inclined members 
shall not exceed three fourths of the depth of beam. It may be assumed 
that all of the external vertical shear in excess of the amount heretofore 
specified as allowable for concrete is provided for by the steel in vertical 
or inclined web members and bent up bars. 

Web members, such as stirrups, when not rigidly attached to the 
longitudinal steel at both top and bottom, shall be carried around and 
bent over the longitudinal members or otherwise sufficiently anchored 
in the compression concrete to develop the tensile stresses existing in them. 
Web members shall be rigidly attached to the longitudinal steel on 
the tension side. Stirrups at the ends of continuous girders shall be 
inverted with the free ends anchored in the compression concrete at the 
bottom of the beam. The length of stirrups or diagonals embedded in 
compression concrete shall be sufficient to develop their entire tensile 
stresses by adhesion. 

COLUMNS 

The length of columns shall be taken as the maximum unsupported 
length. 

The unsupported length of columns shall not exceed 15 times the 
effective diameter or least effective thickness when longitudinally rein- 
forced nor 10 times the effective diameter for hooped columns, and in no 
case shall the effective diameter or least effective thickness be less than 9 
inches, measured within the ties or hooping from out to out of the longi- 
tudinal reinforcement. The length shall include any corbel or knee brace 
attached to the column. The effective diameter of columns supporting 
girderless floors shall be not less than one twelfth the least panel dimension 
of panels supported by any column. 

Bending stresses in columns due to eccentric loads shall be provided 
for by increasing the section of concrete or steel so that the total unit 
stress shall not exceed the allowable working stress in flexure. 

Suitable steel base plates or castings shall be provided at the bottom 
of columns to distribute the loads over the footings, and the vertical rein- 

8 



RECOMMENDED SPECIFICATIONS FOR REINFORCED CONCRETE DESIGN 

forcement bars shall bear squarely on these plates or the reinforcing bars 
shall be carried down into an enlarged footing to distribute the load 
through bond stress. 

In columns where necessary to splice vertical bars having areas in 
excess of IJ^ square inches, it shall be done by cutting the bars squarely 
at the ends and enclosing them in a close-fitting pipe sleeve, or uniting 
them by a threaded splice or other mechanical connection that will transfer 
the load from one to the other without stressing the adjoining concrete 
excessively. The middle point of such splices shall be within 1 foot above 
the floor level. Splices in column hooping where necessary shall be 
sufficient to develop the full strength of the hooping. 

All interior columns shall be round. When interior columns other than 
round are used for architectural effect, the corners shall be made of plaster 
on metal lath built around the columns after they are fully set. 

Longitudinally reinforced columns shall have not less than 4 vertical 
bars or rods secured against lateral displacement by steel ties placed not 
farther apart than 16 diameters of the vertical bars or rods, nor more than 
12 inches. The area of the vertical reinforcement shall be not less than 
1 per cent nor more than 4 per cent, calculated upon the effective area 
of the column, which is the area within the reinforcement. No vertical 
bar shall have a diameter or least dimension less than 5/8 inch and steel 
ties shall be not less than 1/4 inch in diameter or least dimension. 

Hooped columns shall be reinforced with vertical steel with an area 
of not less than 1 per cent and not more than 4 per cent, calculated upon 
the effective area of the column. The vertical bars or rods shall be spaced 
not farther apart than one-eighth the circumference nor more than 8 inches, 
and be secured to the hooping. The reinforcement, in the form of hoops 
or spirals, shall be not less than 1 per cent (that is, a volume of steel equal 
to the required per cent of the volume of concrete within the hoops or 
spirals for a unit length of column), with a clear spacing not greater than 
one-sixth the effective diameter, and preferably not greater than one- 
tenth the effective diameter, nor more than 23^ inches. For hooped 
columns reinforced as herein specified, the unit concrete stresses may be 
700 pounds per square inch for 1: 2:4: concrete and 870 pounds per 
square inch for 1: 1}^: 3: concrete. 

The load which may be carried by any column shall be determined by 
the following formula: 

9 



RECOMMENDED SPECIFICATIONS FOR REINFORCED CONCRETE DESIGN 

P =/, {A, +nJ,) 

in which: 

P = total load in pounds. 

/^ = allowable compressive fiber stress in pounds per 
square inch on the concrete. 

A^ = effective area of concrete in square inches. 

n = ratio of deformation. 

A J = area of vertical steel in square inches. 

Axial compression in structural steel columns thoroughly encased in 
concrete having a minimum thickness of 4 inches and reinforced with not 
less than 1 per cent of hooping steel (that is, a volume of steel equal to 1 
per cent of the volume of concrete within the hoops), equally divided 
between vertical reinforcement and spirals or hoops spaced not more than 
12 inches apart, may be taken at 16,000 pounds per square inch on the net 
section of the structural steel, no allowance being made for the concrete 
casing. The spirals or hoops shall be placed not nearer than 1 inch from 
surface of the concrete. The ratio of length to least radius of gyration 
of the structural steel section shall not exceed 120. 

WALLS 

Exterior and interior bearing and non-bearing walls of reinforced 
concrete shall be securely anchored to all intersecting walls, columns and 
floors, and the allowable compressive stress shall not exceed 250 pounds 
per square inch. The thickness shall be not less than two-thirds that 
specified for brick walls, and in no case less than 8 inches. All such walls 
shall be reinforced with steel running both horizontally and vertically. 
The amount of reinforcement shall be not less than one-fifth of 1 per cent 
of the cross section of the wall, and shall be equally disposed near each 
face of the wall; except that in walls or partitions 8 inches or less in thick- 
ness, the reinforcement may be placed as a single layer in the middle. 
Reinforcement shall be spaced not more than 18 inches apart. Additional 
reinforcement shall be placed around wall openings, and all vertical and 
horizontal reinforcement shall be wired or have other mechanical bond 
at intervals not exceeding 18 inches in either direction. 

GENERAL 

The 1916 Report of the Joint Committee on Concrete and Reinforced 
Concrete shall be followed in the design of girderless slabs, and it shall be 
the final authority in interpreting these specifications and applying same 
to unusual cases of spans and loading. 

10 



Note 

The revised ''Standard Specifications and Tests for 
Portland Cement," of the American Society for Testing 
Materials, which become effective January 1, 1917, will 
be reprinted for distribution by the Portland Cement 
Association. 

These Specifications are the result of several years work 
of a special committee representing a United States Govern- 
ment departmental committee, the Board of Direction of 
the American Society of Civil Engineers, and Committee 
C-1 on Cement, of the American Society forTestinglMaterials, 
in co-operation with Committee C-1. 

The specifications will be available about December 15 
and copies may be obtained by writing the Portland Cement 
Association. 



LIBRARY OF CONGRESS 



019 418 999 

Fundamentals of Reinforced Concrete De- 
sign 

Suggested Specifications for a Concrete 
Swimming Pool 

Suggested Specifications for Concrete Ten- 
nis Courts 

Suggested Specifications for Concrete 
Walks 

Suggested Specifications for Concrete 
Floors 

Specifications for Concrete Roads, Streets 
and Alleys 

Specifications for Concrete Pavement Be- 
tween Street Car Tracks 

Specifications for Portland Cement Stucco 



I 



Are publications which may 
interest you. They ca7i be had 
free of charge on request of the 
Portland Cement Association. 



